1. Field of the Invention
This invention relates to a device for illuminating the walls of a tubular tissue within the body of a mammal and more particularly to a flexible, steerable illuminating guidewire which may be used to deliver light to the walls of a tubular tissue.
2. Prior Art
It is helpful when discussing the prior art relating to the present invention to illustrate state of the art light delivery in the context of a particular medical application such as Photodynamic Therapy (PDT). PDT has been shown to be a very effective method for treating tumors. PDT has also been proposed for the treatment of cardiovascular disease. Light interaction with tissue with or without exogenous chromophores being present has also been proposed as a diagnostic tool employing fluorescence, Raman scattering, and/or Raleigh scattering measurements. Delivery of light from a source such as a laser to the treatment sight is accomplished through the use of a single-fiber delivery system with special light diffusing tips affixed thereto. As the field of PDT matures, new light delivery systems are needed to treat specific sites. One particular need arises due to the inability of prior art light delivery systems to treat the wall of tubular tissue having very small diameter lumen. Extremely flexible prior art light diffusing catheters are normally inserted over a guidewire and, therefore, have a relatively large profile. Others lacking a guidewire lumen, are low profile and relatively rigid and unsteerable.
Examples of light delivery systems for illuminating the walls of vessels within the body include a single fiber, cylindrical diffuser (U.S. Pat. No. 5,196,005); a spherical diffuser (U.S. Pat. No. 4,693,556); a microlensing system (U.S. Pat. No. 5,231,684); and an over-the-wire cylindrical diffusing, multi-fiber-optic catheter (U.S. Pat. No. 5,169,395). An example of a light transmitting diagnostic catheter is disclosed in U.S. Pat. No. 5,217,456 entitled: Intravascular Optical Radial Imaging System by the present inventor. While these catheters have their particular uses in delivering diffuse light to the walls of some tubular tissues of the body, they are not generally suitable for delivery to the walls of very small diameter tubular tissues.
A light diffusing catheter for use in the vasculature of the body is described by Narciso, Jr. in U.S. Pat. No. 5,169,395. This light diffusing catheter delivers therapeutic levels of light to a treatment site located on the wall of a tubular tissue within the body. The catheter is introduced into the body percutaneously and directed to the particular treatment site via a guidewire. The guidewire acts to direct the light diffusing catheter. With a dedicated guidewire integral and coextensive with the body portion of the catheter, the catheter of the present invention need not have the high profile required by a catheter that fits over a guidewire.
A more low profile catheter for delivery of light is described by Doiron, et. al. in U.S. Pat. No. 5,196,005. The catheter described in the '005 patent is relatively low in profile and could be used for delivering light to the luminal wall of small blood vessels but the delivery of light to a particular treatment site is made difficult because of the lack of a steering capability. It is contemplated within the '005 patent that the catheter be delivered to the particular treatment site by means of a standard catheter which is delivered over a guidewire. The catheter has an angioplasty balloon thereupon. The angioplasty catheter can be deployed over the guidewire, the balloon inflated, the guidewire removed and the tissue illuminated. This procedure is cumbersome and most clinicians prefer not to remove the guidewire once a lesion has been crossed, until the procedure is completed.